Dahlia bud and leaf problem

Help!! The buds on my dahlia seem a little worse for wear. Some are black disheveled and taking an age to bloom, the leafs themselves dont look that great either compared to my other dahlias.(see pics)
Any help greatly appreciated.

 

Blimey, that doesn't look good. Have you checked for pests on the foliage/buds? It looks like it's in a pot, so it might be worth knocking it out and checking the roots for pests also. Have you used a weedkiller anywhere near it?